Electric fuse plug



Dec. 11, 1934. s. QUISLING 1,983,993

ELECTRIC FUSE PLUG Filed Oct, 18, 1933 Patented Dec. 11, 1934 UNITED STATES PATENT OFFICE 7 Claims.

This invention relates to improved electrical fuse plugs.

The object of this invention is the provision of a fuse plug which may be manufactured at a price greatly below that possible with the design of fuse plug generally used today.

The invention also contemplates the provision of a fuse plug which will be luminescent or light colored when acting as a conductor, and dark or black when burned out or blown.

Although a preferred embodiment of the invention is shown and described, it is understood that changes may be made within the scope of what is claimed without departing from the spirit of the invention.

In the drawing:

Figure 1 is a side elevation of a fuse plug constructed in accordance with the invention;

Figure 2 is a bottom view;

Figure 3 is a vertical section; and,

Figure 4 shOWs a modified form of the invention.

Referring to the drawing in detail, the fuse plug in outward appearance resembles the present day form of plug and is indicated generally at 1. It will be seen in Figure 3 that the fuse is cast in one piece. Insulating material, preferably glass, is used in its formation, although it will readily be seen that any easily moulded insulating material, such as hard rubber or bakelite may be used. The fuse 1 has the usual threaded portion 2 and a head 3, by means of which the fuse may be readily inserted or withdrawn from a fuse socket.

A positive contact 4, extends below the fuse, and the bottom of the fuse curves upward and outward to the sides. This construction assures contact with the positive side of the current line at the contact point 4 only. The negative side of the line is contacted as usual through the threaded portion 2.

After the fuse has been cast in the desired shape, it is dipped into or painted with a mixture of powdered fusible metal and luminescent or light colored paint to within a short distance of its top as is indicated by 5. It can be seen that this coating of fusible metal will act as a conductor for electric current under normal conditions. Any dangerous overloading on the line will instantly fuse this coating and break the circuit.

By forming the fuse body of glass, and the addition of luminescent or light colored paint to the coating mixture, the condition of the fuse can be ascertained. Certain chemicals may be added to paint causing the paint to glow and appear luminous under normal conditions, but when subjected to heat undergo chemical change and turn dark. Such paint is used in the coating mixture which is applied to the fuse. The type of luminous paint used in my invention is that which contains a mixture of sulfur and the sulfides of the luminescent earthy metals, including calcium, barium, zinc or strontium single or together. This mixture is white or pale yellow and gives off luminescent light as it slowly undergoes oxidation. Oil or lacquer is used as the fluid with which these chemicals are mixed. The fuse plug is dipped in this paint and while still moist and sticky is dipped into powdered, flaked or otherwise, divided metallic magnesium of depth or thickness and width, which will conduct electricity only of given strength without fusing and combining with the sulfur of the sulfide of the paint to form a brown non-conductible magnesium sulfide. Thus the fuse shows a change in color when the magnesium conductor is overloaded as well as bringing about a loss of luminescence of the sulfide of the paint, which undergoes rapid oxidation and chemical change at the temperature generated by this change in the magnesium. Of course it is understood, iron or copper or similar metal which will fuse to form a dark colored sulfide could be used as well as magnesium.

As the top of the fuse body is left free of paint, a glance into a fuse box using a number of these plugs will be suficient to detect which fuse has been burned out.

In Figure 4, is shown a slightly different form of fuse body. This type fuse body has a sunken center portion 6, leaving a comparatively thin bottom. By thus decreasing the thickness of glass a much better view of the bottom may be obtained and material is saved in manufacture.

Having thus described the invention, what I claim is:

1. In a fuse plug, a solid threaded insulating body, the lower portion being externally coated with paint containing luminous sulfides of earthy metals with an outer coating of metal capable of fusing to combine and form a dark colored sulfide adherent thereto.

2. In screw type fuse plug, a transparent insulating body portion, the lower portion first coated with luminescent paint containing sulfur and sulfides and externally with metallic magnesium or other metal of given depth and shape, which metal will fuse resulting in formation of compound showing colorimetric change due to sulfide being formed when current passing through said metal is overloaded.

3. In a fuse plug of screw socket type, a solid body portion of transparent insulating material, a coating of luminescent paint containing sulfur or luminescent sulfides, and metallic magnesium adherent to the outer side of this paint to fuse and combine with sulfur forming a brown magnesium sulfide, if the current it conducts becomes above a certain strength.

4. In an electric fuse plug of screw socket type, a transparent insulating material forming the body of the plug, visibly coated on the under surface where contact is made with the live terminals of an electric circuit, with a luminescent paint containing luminescent sulfides and sulfur within and adherent metallic magnesium without which metallic magnesium will fuse and break the circuit when too strong a current passes through it, also produce chemical colorimetric and luminescent changes. I

5. In a device of the character described, a transparent core of insulating material formed to fit the socket of an electric fuse; a coating of luminous paint containing sulfur and luminescent sulfide with adherent metallic magnesium of definite amount and thickness adherent thereto, which metal will fuse when currents of given strength pass through it.

6. In a device of the character described, a screw plug of socket type made of transparent insulating material, the lower end of which is coated with luminescent paint containing metallic magnesium so arranged that this magnesium contacts positive and negative terminals of an electric circuit, which metal coating is of depth and width directly proportional to capacity of fuse desired.

7. In a device of character described, a cup shaped transparent, screw plug of insulating material coated on the outer lower end with a paint containing luminescent sulfides and sulfur with metallic magnesium adherent thereto in a coating 'of width and depth proportional to strength current from which protection is sought.

SVERRE QUISLING. 

